As a material of construction, copper and copper alloys constitute one of the major groups of commercial metals. They are widely used due to their combination of physical properties which include electrical conductivity, thermal conductivity, corrosion resistance, machinability, fatigue characteristics, workability, formability, and strength. In addition, copper alloys can be made in a variety of colors, are non-magnetic, and can be finished by plating or lacquering. Most copper alloys can be welded, brazed or soldered with little difficulty.
To improve certain of these basic properties, the various alloying elements can be selected. Zinc has been found to be a particularly useful element and a number of commercial copper-zinc alloys include the family of brasses. Yellow brass for example, an alloy of 65% copper 35% zinc is useful due to its golden color and good workability. Due to its relatively low melting temperature and compatibility with most steels and copper alloys, the brasses were also used as brazing alloys to join these different base metals together. Today there are a multitude of copper-zinc base brazing alloys containing a wide variety of additional alloying elements for particular applications.
One particularly effective elemental additive is nickel, and the family of copper-zinc-nickel alloys are known as the nickel-silvers due to their whitish appearance. Typical compositions of nickel-silver alloys range from 55-65% copper, 17-27% zinc and 15-20% nickel. While having a higher melting temperature than the brasses, the nickel-silvers provide compatibility with a number of other materials, such as tungsten carbide, and also provide higher strength.
A very popular family of brazing alloys include those containing silver. Such silver-copper-zinc (and optional nickel) brazing alloys have been used for joining carbide compounds to various substrates because of their relatively low melting temperatures (approximately 550.degree.-750.degree. C.). While these alloys exhibit good bonding strength, sufficient plasticity and highly preferred brazing temperatures, they are expensive due to the silver content. Also, higher joint strengths and better high temperature properties are desireable. Therefore, substitute alloys have traditionally been sought by those skilled in the art for brazing carbide components to various substrates.
One family of alloys which has been suggested as substitute for such silver-base or nickel-silver alloys is the copper-nickel-manganese-family. Typically, such alloys contain about 50-55% copper, 8-11% nickel and the balance manganese. These brazing alloys are relatively free flowing and compatible with various carbides and base metals such as cast irons, steels and tool steels as well as some stainless steels and nickel-base alloys. However, since zinc is not included in this family of alloys, the alloy melting temperature ranges from about 850.degree. C. to about 930.degree. C. Therefore, brazing temperatures on the order of about 950.degree. to 1050.degree. C. are required to produce suitably brazed joints.
Applicants now have found, however, that copper-zinc-manganese-nickel alloys provide compatibility with a variety of carbide compounds and substrates, and comparable strengths and fluidity in comparison to the copper-manganese-nickel alloys of the prior art while decreasing the brazing temperature to a lower range. In comparison to silver alloys, the alloys of the present invention provide improved strengths at much lower cost in addition to providing compatibility with a wide range of carbide compounds and substrates.